This happened in Metz, France. You hear them shouting "Islam hors d'Europe!" [Islam out of Europe] while the mob shouts "Fachos!" [Fascists].
They hold up a banner saying "Expulsion of Islamists" then shout "Terrorists out of Europe".

At first the police seem to protect the demonstrators then suddenly move against them, pushing them back. It's not clear what triggers this. Several people are then arrested. It looks like they are members of the patriot group, although it's not clear. The crowd seems to cheer the arrests.

Most members of the crowd look like ordinary middle-aged people, rather than dedicated leftists, although someone is waving a (Palestinian?) flag in the background. Hard to be sure whether this is just the suicidal altruism that has been inculcated into ordinary Europeans or hardcore, organised leftism.

It looks like this started as a ceremony arranged in homage to the victims of the attacks in Paris.